Electrolytic decomposition of saline solutions.



PATENTED JUNE 27, 1905.

A. B. LAEOHAR. ELECTROLYTIC DECOMPOSITION OF SALINE SOLUTIONS.

APPLIOATION FILED OCT. 9, 1902.

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A. B. LAROHAR.

ELECTROLYTIC DECOMPOSITION OF SALINE SOLUTIONS.

APPLICATION FILED OGT.9, 1902.

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PAIBNTED JUNE 27, 1905.

A. B. LAROHAB.

ELECTROLYTIC DECOMPOSITION OI SALINE SOLUTIONS.

APPLICATION FILED OCT. 9, 1902.

fizz nesies (Ma/W NITED STATES Patented June 27, 1905.

PATENT FFICE.

ARTHUR B. LARGHAR, OF OLDTOIVN, MAINE, ASSIGNOR TO PENOBSCOT CHEMICAL FIBRE COMPANY, OF MAIN E.

ELECTROLYTIC DECOMPOSITION OF SALINE SOLUTIONS.

SPECIFICATION forming part of Letters Patent No. 793,138, dated June 27, 1905.

Original application filed October 9, 1900, Serial No. 32,482. Divided and this application filed October 9, 1902. Serial No. 126.402.

To all whom it 'nmq concern:

Be it known that 1, ARTHUR B. LAROIIAR, a citizen of the United States, and a resident of Oldtown, county of Penobscot, and State of Maine, have invented a new and useful Improvement in the Electrolytic Decomposition of Saline Solutions, of which the following is a full, clear, and exact description.

The object hereof is to secure an invention in the art or process of electrolytic decomposition of saline solutions which may be carried out, and preferably is carried out, by the apparatus described in my application, Serial No. 32,182, filed October 9, 1900, of which this is a division.

I will first describe such apparatus with reference to the accompanying drawings, in which- Figures 1, 2, and 3 are plan views of the cell with portions broken away, Fig. 1 representing the cover on, Fig. 2 representing one end of the cell with the cover and the upper portion of diaphragm removed, and Fig. 3 being a horizontal section of the opposite end, taken in the plane of the top of the tank and omitting the diaphragm. Fig. A is an isometric view of the cover. Fig. 5 is a vertical longitudinal section on the line .0 a of Figs. 1, 2, and 3. Fig. 6 is a cross-section on the line ;1 of Fig. 1.

a is a tank, preferably of steel boiler-plate, which is open at the top and is large enough to provide a reservoir surrounding the cell.

The cathode is of peculiar and novel construction. It consists of a grating forming substantially a complete inclosure constituting the side walls of the cell. As shown in the drawings, this grating is in sections, Zr, 7), 6 and 12 forming the four sides of a parallelogram and secured together at the corners by posts 0, and 0', preferably of square bars. I prefer that each section of the grating should be substantially plane, so that when combined they form a polygonal inclosure, which serves not merely as the cathode, but possesses suflicient rigidity to act, in conjunction with the corner-posts, as the wall of the cell, supporting itself and the diaphragm which is stretched upon it, and in the example shown also supporting the upper portion or 5 cover of the cell, from which the anodes depend.

The grating composing the cathode consists of a series of bars or slats (11], &c., preferably of soft steel. Each of these slats is oblong in cross-section (say [ive-eighths inch wide by .065 inch thick) and stands, preferably, vertically and preferably substantially at right anglcs to the plane of the wall, of which it forms a part. The slats are spaced uniformly apart (say .035 inch between every two slats.) These spaces constitute passages or channels leading outward through the cathode from the diaphragm.

As shown, each passage or space is longer 5 measured from the diaphragm outward than its width measured between adjacent slats. As shown also, each passage is, excepting for the presence of the connecting-bolts and washers, substantially continuous from the lower to the 7 upper portions of the cathode. The slats on each side of the cell are shown as held in the described position-by a series of bolts or rods 0 c c c 0', extending through two iron posts and all of the intermediate slats. \Vashersf are placed on each rod between every two slats, maintaining the proper distance apart. By having all the slats of equal thickness and all the washers of equal size a substantially uniform grating may thus be constructed, extending substantially without break or interruption all the way around the cell, so that with respect to the size of the cathode and the surfaces thereof exposed and the passages thercthrough the brine, percolating through 5 the diaphragm, may meet with substantially uniform conditions in all directions.

By the above construction a lamellar cathode is formed which acts to divide the liquid into a great number of films, which pass from 9 the diaphragm out through the cathode into the receptacle which surrounds the cathode. in the course of this passage the liquid by be ing in films is brought in most intimate contact with the layers of the cathode. At the same time the position of the passagessubstantially radiating on all sides from the anode-compartment to the outer compartment is most favorable to the free and direct circulation of the liquid and the escape of the gas.

The floor of the cell is shown as being constructed of a series of angle-irons g g, 850., extending horizontally and transversely across from the bottom of the grating on one side to the bottom of the grating on the opposite side, each end of each angle-iron being secured in place between the lower ends of two slats by the bolt a, by which the lower ends of the slats are combined.

h is a layer of Portland cement filling the spaces between the angle-irons g and between the lower ends of the slats, so as to form a continuous smooth floor.

The diaphragm consists, preferably, of asbestos paper, several thicknesses of which 2'" i c' say three or four thicknesses-are placed around the walls of the cell so as to break joints with each other, each layer forming a lap-joint with itself. The lower edge of the diaphragm is turned inwardly, so as to lie upon the cement floor, as shown. jis a layer of sand which covers the cement floor and extends over the lower edges of the diaphragm. At its upper edge the diaphragm is supported by the upper ends of the cathode-slats (Z, over which it is folded outwardly and downwardly and against the outer edges of which its edge is secured by a surrounding frame 70. The cover Z, preferably consisting of a flat slab of slate, rests on the diaphragm, where it is folded over the tops of the slats, and the space on between the edges of the cover and the frame In is preferably filled with cement.

The anodes consist, preferably, of a series of graphitized carbon slabs n n, &c., which extend downwardly through holes in the cover Z, in which they are properly luted. At their lower ends they may rest upon the sand layer j. Each anode is preferably inclined from top to bottom toward the diaphragm-wall adjacent to it for the purpose of making the length of the passage for the current through the electrolyte longest where the resistance of the carbon is least, and vice versa. In practiceI have so inclined the anodes that the bottom of the anode was about one-eighth of an inch from the adjacent diaphragm-wall, while the top was about five-eighths of an inch therefrom.

Brine is supplied to the interior of the cell through the hard-rubber pipe 0 froma trough p, of non-conducting material, in which trough the brine from a reservoir 9 is kept at a substantially constant level by the centrifugal pump 7* and the overflow-pipe 9-. In this way the surface-level of the brine within the diaphragm is kept substantially at the line .2 leaving a sufficient space between the brinesurface and the cover for the free escape of the chlorin gas to the pipe 8, through which it passes to any suitable receiver. The interior of the cell above the brine-level is lined with lead for protection against the action of the chlorin.

The caustic-soda solution escapes from the reservoir in the tank a around the cell through the pipe 6 from an overflow-pipe 25, extending upwardly in said reservoir. Said overflow-pipe is pivotally secured at its lower end, so that its overflow intake or mouth may be adjusted at various elevations in the dotted'line t so as to permit the operator to adjust the surface-level of the liquid contained in the reservoir outside the cell relatively to the surface-level of the brine inside the cell. By this adjustment I utilize a very moderate and regulatable hydraulic pressure to gently press the liquid through the diaphragm in opposition to the tendency toward backward diffusion of caustic soda, while avoiding any degree of pressure which would produce such rapidity of percolation as to cause an undue escape of unconverted salt through the diaphragm and cathode-passages.

I have discovered that with an apparatus constructed substantially as above described I can by the simple adjustment relatively of the surface-levels of the liquids, so as to maintain the inside level slightly above the outside level, secure conditions under which backward diflusion through the diaphragm of the caustic soda is substantially prevented, the escape of unconverted salt through the diaphragm is small, (i. a, less than about fifty per cent.,) and an approximately theoretical efficiency is attained, accompanied by great durability of the diaphragm and other portions of the apparatus. In my experience with a comparatively new diaphragm I have found that with a total depth of brine of about twenty-four inches a difference in level of about one and one-half inches between the level .2 inside of the cell and the level .2 outside of the cell was sufficient to accomplish these results. The said adjustment also enables me to increase at will the pressure tending to produce percolation of the brine through the diaphragm. This is of the ut most importance. Efiiciency requires that the rate of percolation be maintained; but the opposition of the diaphragm to percolation increases in use because of the deposit of impurities from the brine and of particles of anode carbon. By the adjustment of the liquid-levels it is constantly Within the power of the attendant to compensate for the obstruction of such deposits, and thus prevent waste of power.

Positive electric conductors are connected with the anodes and negative electric conductors with the cathode in any efficient manner.

In starting the cell is partially filled with brine and the reservoir in the tank around the cell is partially filled with water. The electric current being turned on, the brine is decomposed, the chlorin thereby generated rising to the top of the cell and passing off through the pipe s to a tank or tower suitably arranged for its absorption. The metallic constituent of the brine combines at the passages through the cathode with the water there present, forming a solution of caustic alkali. The hydrogen liberated in said passages passes freely up through the same and escapes at the open top of the tank. To enable a person skilled in the art more readily to reproduce my said results, I will add the following concrete data as to the conditions under which I have operated with an apparatus constructed as above described: There were fourteen hundred slats, each of the dimensions stated; twenty-two anodes, each one and one-fourth inches by four inches in crosssection; twenty square feet of diaphragm composed of three plies of asbestos paper, each one thirty second inch in thickness. The height of the cell was about thirty inches and the depth of brine therein about twenty-four inches. I used six hundred amperes of current at 3.8 voltage. The distance from the top of each anode to the adjacent side of the diaphragm at the top was about live-eighths of an inch and the distance at the bottom about one-eighth of an inch. Under these conditions I secured the best results by maintaining the level of the liquid inside the cell about one and one-half inches above the level outside the cell.

The space a within the series of anodes, which receives the supply of electrolyte through the pipe 0, constitutes a common reservoir of electrolyte, which [lows thence in all lateral directions through the spaces between the anodes into the space 14 traversed by the electric current. The presence of this common reservoir 4, from which the pressure above referred to is constantly tending to cause the electrolyte to flow through the sides a. and the diaphragm and the cathode into the containing-tank, constitutes an exceedingly important factor in maintaining in all parts of the apparatus where the electrolysis is taking place a uniformity of conditions and action consistent with the highest degree of efficiency and uniformity of the product. As preferably constructed, the reservoir (1 is of sullicient capacity to exceed the capacity of the space 1/". The reservoir (1 also provides a desirable place within which to add, if desired, salt to the electrolyte sufficient to compensate for any loss of concentration which may occur.

I do not in this application lay claim to the apparatus herein described, since the same is the subject of application Serial No. 32,482, hereinbefore referred to.

I am aware that it has heretofore been proposed to maintain an excess of pressure due to a higher level of the liquid in the anodecompartment than in the cathode-compartment; but it has remained for me to discover that the efficiency of the apparatus can be increased and the passage through the diaphragm of caustic soda and undeeomposed salt limited by regulating or controlling this excess of pressure and to provide means for such regulation.

Having thus described my invention, I claim as new and desire to secure by Letters 1atent 1. The improvement in the electrolysis of saline solutions by the use of a diaphragm immersed in and separatingtwo bodies of liquids, one containing the anode and the other the cathode, which consist-s in regulating the depth of the cathode-containing liquid relative to the liquid in the anode-ehamber to control the passage of caustic soda and undeeomposed salt through the diaphragm and prevent the backward diffusion of the caustic soda through such diaphragm.

2. The improvement in the electrolysis of the saline solutions by the use of a diaphragm immersed in and separating two bodies of liquid, one containing the anode and the other the cathode, which consists in controlling the passage of caustic soda and undeeomposed salt through said diaphragm by the regulation during the operation of the depth of the cathode-containing body of liquid, and conducting the liquid, percolating through the diaphragm, in films or thin sheets of liquid by passing the latter through narrow passages extending through the cathode as and for the purpose set forth.

In testimony whereof Ihave hereunto signed my name in the presence of two subscribing witnesses.

A RTH UR B. LARUHA R.

\Vitnesses:

Coimuttx M. I'IILLTARI), ALVAII L. H INCKLEY. 

